| Wheat root diseases are foot and root rot diseases caused by soil-borne fungi. Since 1990, the wheat root diseases have occurred severely and become a major obstacle for wheat production in Hebei province. Disease investigation was made first by inquiring letters from plant protection station of each county in Hebei province from 1998 to 1999. The data about the occurrence of wheat root diseases from 54 counties were collected since 1980. By investigating wheat root diseases in different counties (Yongnian, Cixian, Quzhou, Guantao, Longyao, Linxi, Ningjin, Yaoyang, Zhengding, Xinji, Luanxian) in Hebei from 1999 to 2001, and visiting experts, the occurrence and characteristic of wheat root diseases were obtained. Based on weather conditions of 113 counties from 1985 to 1998 and the types of soil in different ecological areas, the distribution areas of different root diseases such as sharp eyespot, common root rot and take-all were classified by means of cluster analysis. The conclusion was that the occurrence trend of wheat sharp eyespot and common root rot disease in south of Hebei is severer than in the north. Handan and Xingtai is the main damage area, Shijiazhuang, Baoding and Langfang are the moderate damage area, Tangshan and Qinhuangdao is the light damage area. Take-all disease of wheat distributes in some counties of Tangshan, Shijiazhuang and Baoding. Based on root disease investigating in different growth stage and in different ecological area, the resistance of main wheat varieties in Hebei province was quite different. The high-susceptible varieties are Wenmai-6 in Handan, Shi-97-6365 in Shijiazhuang, Jimai-36 in Baoding and Jingdong-8 in Tangshan. The middle or high- resistance varieties are Han-4589 and 5316 in Handan, 9541 in Shijizzhuang, 71-3 in Baoding and H3007 in Tangshan. There are more than 400 samples cofleted from different areas in Hebei such as Handan, Yongnian, Cixian, Quzhou, Guantao, Longyao, Linxi, Ningj in, Yaoyang, Xinji, - 48 - Zhengding, Luancheng, Baoding, Anxin, Tangshan and Luanxian. 3772 tissue numbers were isolated in lab, and 2555 colonies were obtained. The main strains were identified. The growth and way of spore-germination of each fungus was observed by grass- covering method. The diameter and the growth rate of hypha, the time of sclerotium appearing of Rhizoctonia spp. were observed. The phialospores and hyphodia of Gaeumannomyces graminis var. tritici were used for fungus identification. The ascus and ascospore were induced by keeping moisture and illuminating of scattered light. Fusarium spp. were cultivated in PSA medium for observing feather and rate of hypha growth, type of spore-germination. Spores were induced by cultivated in wheat seed medium and inoculated in soil. The other strains were cultivated in common medium. The main strains were tested for their pathogenicity. The result showed that there are 12 species pathogens of wheat root diseases in Hebei province. Among them, the most common pathogen is Bzpoloris spp., The distribution of Rhizoctonic spp. is widespread, but its appearing frequency is less than Bipoloris spp. Although the distribution of Gaeumannomyces graminis var.tritici is limited, its harmfulness is rather serioug. The variety and appearing frequency of pathogens are quite different in different areas and different growth stages. The inhibition effects of plant extracts TS-26 and TS-90 against the main pathog...
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